1. Field of the Invention
The present invention relates to a mining apparatus for the mechanized breaking-down of mineral raw materials, particularly coal, in underground mining operations. The mining apparatus includes at least one revolving endless chain and chain wheels for the endless chain at the revolving ends of the chain. A main drive is provided for one of the chain wheels and an auxiliary drive is provided for the other chain wheel. The main drive and the auxiliary drive each have a transmission unit including main transmission stage, initial transmission stage, coupling and drive motor. The initial transmission stage of only one of the auxiliary drive or of the main drive is constructed as a superposed transmission unit. A superposed motor constructed as a controllable electric motor having a small power is connected to a superposed input of only this superposed transmission unit. An auxiliary transmission unit in the form of a worm gear transmission is arranged between the superposed transmission unit and the superposed motor.
2. Description of the Related Art
In mining apparatus of the above-described type it is desired that the drive motors of main drive and auxiliary drive run synchronously because only a synchronous running ensures a uniform load or maximum power of main drive and auxiliary drive. The above-described mining apparatus, or its drive control, is described and claimed in applicants' pending application Ser. No. 07/268,088 filed Nov. 7, 1988, now U.S. Pat. No. 4,921,307, and is used to avoid overloading of either the main drive or the auxiliary drive.
Thus, in accordance with this mining apparatus, only a unilateral control of either the auxiliary drive or of the main drive with the use of a single superposed transmission unit and a single superposed motor, i.e., an electric motor having small power, is necessary. Nevertheless, a synchronous running of the two drive motors is ensured. As a result, with respect to the two chain wheels, a uniform load of the two drive motors and, consequently, a uniform distribution of the load to the chain wheels or the endless chain are obtained. In the above-described mining apparatus, the rate of rotation of the motor can be increased or decreased during synchronization.
The above-described mining apparatus, or the drive system thereof, has been found very useful, however, further improvements are possible. This is because when the mining apparatus operates, inevitably impact and percussion-type loads occur which emanate from the mining device, for example, a coal planing device, and which are transmitted on the driven side into the controlled auxiliary drive (or the main drive). Such impact and percussion-type loads are eventually transmitted to the worm gear transmission unit and there must be absorbed by the drive worm which laterally meshes with the superposed transmission unit. In extreme cases, this may lead to damage of the worm gear transmission unit or of the drive worm thereof and may consequently lead to interruptions in the operation of the mining apparatus.
It is, therefore, the primary object of the present invention to provide a mining apparatus for the mechanized breaking-down of mineral raw materials, particularly coal, in underground mining operations, in which the above-described disadvantages are eliminated. In addition, it is to be safely avoided that damage occurs to the worm gear transmission unit or the drive worm thereof due to impact or percussion-type loads introduced at the driven side, so that the operation of the auxiliary transmission unit is completely trouble free.